Fixing a GEC BT 302 Television

[19Seventy7]

Then I'd suspect that it's over heated, and will most likely need replacing, now.

I'd also go back and trace all the components prior to the resistor, to find out what made it overheat.

Not 100% sure so i'll leave it to the experienced people, but it may give you a starting point.

Good luck
'77

[deepspacedaz]

Thankyou

[PortugalTV]

if the problem was the heater snubber cap it either would have blown apart or blown a tube filament. seems like none of that happened. i think its the resistor that smoked

have you posted a schematic so we can better help?...that resistor overheated for a reason, there is a short somewhere. dont insist with the set until you figure it out. could be a solder splash like someone mentioned, has happened to me a couple times.

[deepspacedaz]

Yes I thought it was the resister as well

[deepspacedaz]

I have posted a scematic

[Station X]

Circuits are attached to post #29

[Heatercathodeshort]

Darren, you have to be able to read a circuit to get anywhere with this.
R41 a 470 ohm 2watt resistor supplies the anode and screen of the sound output valve V9. It is decoupled by a 32uf electrolytic capacitor C87, a dual can combined with C86.

I expect C87 has gone short circuit or the sound output valve has developed a severe short but I suspect the cap more than the valve.

We should have moved on from the frame timebase by now. The last thing we need is you pulling the I.F. board out and creating more problems.

I would suggest you cut one end of R41 removing the H.T. supply to the shorted capacitor. The shorted cap is probably why you are not getting any response from the speaker.The 302 will now run without the resistor overheating but of course there will be no signs of any sound! look at the circuit and you will see the problem.

You can then recheck all your work on the timebase board. Until you get a full raster there is no point in continuing with other non related faults. John.

[HurtyAC]

Hi Daz, First remove power from the set. Remove valve V9 and put it aside. With your meter set to ohms measure the resistance of pin 9 of V9's base to the chassis and then pin 7 to chassis and post the readings here.

[deepspacedaz]

Hello John i snipped the resister and rebuilt the timebase

[deepspacedaz]

Ok The lines are the same maybe a bit larger than before. No smoke after snipping the resister. vert hold and horizontal seem to be working. flashing picture, clicking sound turning up vertical it gets louder dot seems to shake on switch off. INSTALLED NEW VALVES.

[Heatercathodeshort]

Picture please. Rebuilt? What did you do? tell us!

[deepspacedaz]

The picture has not changed since the lat one I sent I just up the parts back changed valves and snipped ressiter

[deepspacedaz]

Looks like this

[deepspacedaz]

with a little static

[Heatercathodeshort]

There is not a lot of point in continuing with this Darren because we have arrived at a dead halt. As a last resort I would suggest you forward the panel to me for checking over but this is not going to cure other faults that may be on the I.F. panel.

To be fair I think this was too big a project for a beginner especially as you are not conversant with circuit diagrams and the confident use of your multi meter.

We both tried hard but I think it's just a project too far. John.

If you do send the panel, remove the valves and write the address label with the aid of a computer to avoid loss in the post. John.

[dazzlevision]

Originally Posted by Heatercathodeshort

If you do send the panel, remove the valves and write the address label with the aid of a computer to avoid loss in the post. John.

Printed circuit boards like these are rather fragile, so it is ESSENTIAL to wrap them in several layers of bubble wrap or similar soft cushioning material - in addition to using a stout cardboard box - securely sealed and clearly addressed.

If not and it is damaged (or lost in the post), it will be very difficult to find a replacement.

[deepspacedaz]

Hi John just to let you know I only added the vertical so far

[Station X]

I'm sure the many followers of this thread want to see this TV working.

You've done your very best, but a TV, even a vintage one, is a complex piece of kit, the repair of which may not be easy.

John is one of the forum's vintage TV experts. Why not avail yourself of his offer to check out and if necessary repair the PCB for you. Then you'll know that that part of the TV is working correctly and you can look for faults elsewhere in the set.

You might wish to include the UY85 valve from the Westminster record player in the package so that John can test if for you and that repair can be progressed too.

[deepspacedaz]

Good idea and thanks

[Restoration73]

I have not much to add, but OT has not specified which converter or vhf signal source
will be used - for both servicing and using the set.
Note the Trader etc sheets often cover the bare minimum of data for the trade engineer.
The actual GEC manuals for these sets are excellent. I would also recommend looking
at the articles "Servicing TV Receivers" in Practical Television magazine issues
January&February 1972 where this set is well covered (also available online pdf)